The invention relates generally to a method and apparatus for providing an inert gas atmosphere to a welding location. More particularly, the invention relates to a method and apparatus for providing an inert gas shield within an interior of a conduit that is being welded.
Metal inert gas welding is a semi-automatic or automatic arc welding process in which a continuous and consumable wire electrode and a shielding gas are fed through a welding gun. Metal inert gas welding is applied to steels because it allows for lower welding time compared to other welding processes. The cost of an inert gas such as a noble gas is high, but regardless, this technique is the most common industrial welding process, preferred for its versatility, speed and the relative ease of adapting the process to a variety of manufacturing situation.
When welding two sections of pipe, the interior portion of the pipe is filled with an inert gas, such as argon. The application of this inert gas is to prevent oxidation at the welding site. To achieve optimal weld quality, a weld bead must be shielded with a protective atmosphere to protect it against detrimental effects of oxidation prior to, during, or subsequent to joining the metal components. Accordingly, a continuous flow of gaseous flux is typically applied to the joining location to expel the ambient atmosphere to prevent oxidation and thereby promote better union of the metal components. Such gaseous flux typically involves a shielding gas composed of a chemically inert gas such as the noble gases helium and argon. During welding, the gaseous flux protects the work from oxidation, and cleans or catalytically enter into the reaction between the materials being united. Therefore, the welding torch, or a separate gas nozzle, typically blasts the top surface of the weld bead with a continuous stream of shielding gas.
However, this technique requires a closed environment for containing the gas within the pipe, using masking tape, pipe plugs, etc. This is inefficient and obtrusive for the welder and pipe fitter spot-welding the two sections of pipe together during the initial fit-up stage of joining the pipe. Further, a great deal of inert gas is used to fill the entire pipe, which is both expensive and unhealthy for the welder and pipe fitter.
Many have attempted to reduce shielding gas waste in the past. One attempt is a delivery hose with a gas surge-restricting orifice at the gas solenoid end of the hose. Another suggestion is a porous diffuser in a weld shield to deliver the gas to the weld path. Another proposal is a series of removable orifice bodies which may be threaded into a valve body. One suggestion is not to fill area around the weld bead, but to merely blast the target weld path with gas.
While the above mentioned methods and apparatus may be suitable for the particular purpose employed, or for general use, they would not be as suitable for the purposes of the present invention as disclosed hereafter.